Triplet-type objective lens



OR awgsw ID April 15, 1969 P. L. RUBEN 3,438,696

TRIPLET-TYPE OBJECTIVE LENS Filed Jan. 23. 1967 PAUL RUBEN INVENTOR.

24mm 219 7 fw aflj ATTORNEYS United States Patent 3,438,696 Patented Apr. 15, 1969 3 3 96 EXAMPLE 2 TRIPLET-TYPE OBJECTIVE LENS [Equivalent Focal Length=100 mm. t/1.6] Paul L. Ruben, Penfield, N.Y., assignor to Eastman Kodak Company, Rochester, N. a corporation of New Thicknesses Jersey 5 en ND V Radil (mm) an Filed Jan. 23, 1967, set. No. 610,883 spacings (mm.)

Int. Cl. G02b 9/14 US. Cl. 350-226 7 Claims Sm? R 7 o= I 1. 75 50.6 h T1=19.2

R2= a71 51:10.7 ABSTRACT OF THE DISCLOSURE H 1 72 29 3 Ra= -95.5 T 323 A photographic objective of the simple triplet type is R4=42.0 2 disclosed which is well corrected for high relative aper- 35:6, 82:5; tures and is particularly suited for use in motion picture III 1. 75 50.6 T3=27.4 cameras. Rl= 67.9

This invention relates to improvements in photographic ob'ectives of the sim le tri let t e havin a bi h relative ap erture. p P W g g EXAMPLE 3 An object of this invention is to provide an improved [Eqmvalent =100 mm. t/Ls] simple triplet type of photographic objective, having a relative aperture of at least f/ 2.7, which is well corrected Lens ND v Raw Thie lggesses for spherical and chromatic aberrations, coma, astigmaspacings (111111.) tism, flatness of field, and is particularly suited for use on motion picture cameras. Stop Sn=10.7 Further objects and advantages will be found in the de- I 1 70 56 2 R1=64.3 T :21 4 tails of construction disclosed in the accompanying ex- R2: -293 l amples and drawing. R3: 31:3 The present invention comprises triplet objectives hav- II 1.67 32.0 T2=21.4 ing two outer positive biconvex elements and an inner 34:4 52:6 71 negatigepbico ncave element. The inner negative elements R =86.9 of the triplets of this invention are as thick as, and in m L70 R 4 most embodiments thicker than, the positive elements. These thick negative elements are used to balance astig- 35 matism and provide additional negative power without an excessive increase in spherical aberration. The lenses of In the above three examples all elements are formed i z gg sg have then dlaphragms located m from from glass having a high index of refraction N to reduce spherical aberration. The middle negative elements The drawmg shows a cross sectlonal View of an objec' 40 have lower indexes of refraction than the sitive eletiveleinbodying the invention with the long conjugate on ments to flatten the fi e1 d Po the e t.

The objective in the drawing comprises three airspaced simple lenses, designated I, II and HI. The outer two EXAMPLE 4 lenses I and III are positive biconvex elements, and the 5 [Equivalent FocalLength=1mn1m m7] inner lens II is a thick negative concave element. The diaphragm is located in front of lens I. Thicknesses Numerical data for constructing seven embodiments of Lens N V Radii (mm.) and photographic objectives according to the invention as outspacin s (mm.) lined above is given in the following examples in which the lens elements are numbered from front to rear, N is RG45, the index of refraction of the lens elements for the D line, I 1. 49 57.4 'Ii=14.0 V is the index of dispersion, and R, T and S refer respec- R2: 31:41 tively to the radii of curvature of the lens surfaces, the Ra= 59.9 thicknesses of the lens elements and the airspaces between H 34:41, the elements, numbered by subscript from front to rear. R 718 2=4.71 EXAMPLE 1 III 1.61 58.8 5 T3=23.7 [Equivalent Focal Length=100 mm. i/LG] Thicknesses 6o Lens ND V Radii (mm.) and spacmgs (mm) Example 4 is an embodiment of this invention in which the front two components are formed from plastic and the third component is formed from glass. The use of plastic- I 1.75 50.6 Ti=18.6 5 glass combinations in triplets is disclosed in US. Patent "1893 sl=7 43 3,194,116 in which the negative element is formed from a= -90.3 a copolymer of acrylonitrile and styrene having an index H 34:4 TF4; of refraction N about 1.56 and index of dispersion V z= about 37. To balance the effect of thermal expansion, one In 1.75 50.6 TF2 7 of the positive elements is formed from a plastic, prefera= ably methylmethacrylate having an index of refraction N about 1.49 and an index of dispersion about 57.

EXAMPLE 5 ifngs bfetween the lens elements, numbered by subscript [Equivalent Focal Length=100 mm. 1 21 mm mm to rear Thieknesses L Lens N V Radii (111.111.) an 5 ens ND 1 V Rad a ifi gi iiiii s Spacmgs (mm.)

R =.729F Stop o= I 1. 75 50.6 I T =.l86F

R|=53.5 Rg=1.90F I r. 1.61 57.2 T1=l7.0 Slam;

1= 11 1.12 20.3 T2=.486F R3= -69.5 R,=.4s4F 1r 1. 65 33 8 T2=1-5 8220191 R =42.5 R5=.750F

z= III 1. 75 50.6 T3=.229F R5=7L8 R9=.750F III 1.61 57. 2 T1=1s,4

2. A photographic objective of the simple triplet type having an equivalent focal length F and comprising two outer simple positive biconvex lens elements and an inner simple negative biconcave lens element, the lens elements EXAMPLE 6 [I having substantially the following characteristics and spa [Equmlent Length=1 m] tial relations in which the lens elements are numbered Th1 k from the front, N is the index of refraction for the D Lens ND V Rad (mm) ff line, V is the index of dispersion, and R, T and S refer p gs respect1vely to the radu of curvature of the lens surfaces, the axial thicknesses of the lens elements, and the axial Stop R So=14.8 spacings between the lens elements, numbered by sub- 1 L 61 6 TF1 script from front to rear:

Rg= 152 R 69 I S1=6.29

Lens N]; V Radu Ttncknesses II 1.65 33.9 R4=39l5 T1 19.6 I and spacings R 682 Sz=7.4 5: R 687E III 1.61 58.6 Ta= 8- I L75 50 6 T 1923. Br: 61.4 R2 3.71F S1 107E Ra=.955F

II 1. 72 29. 3 T2=.323F

R =.420F R 679! S2=.056F EXAMPLE 7 III 1. 75 50.6 T3=.274F [Equivalent Focal Length=l00 mm. f/2.7] 40 Ra=-.679F

Th1 k 1 Lens ND V Radii(n1m.) an 3 A photographlc ob ective of the simple triplet type spamgs (min) having an equivalent focal length F and comprising two outer simple positive biconvex lens elements and an inner p R1=52 o simple negative biconcave lens element, the lens ele- I 61 5 ,6 T=15.7 ments having substantially the following characteristics RP 31:13 and spatial relations in which the lens elements are num- ,4 bered from the front, N is the index of refraction for H RF" 6 the D line, V is the index of dispersion, and R, T and S s1=2.9 refer respectively to the radii of curvature of the lens m 1 61 58 6 R5=135 TF1, surfaces, the axial thicknesses of the lens elements, and R|= 69.7 the axial spacings between the lens elements, numbered by subscript from front to rear:

Lens ND V Radii Thicknesses In the above examples, 5, 6 and 7, all elements are and spacings formed from glass, as in the first three examples. R 6433 Although the invention has been describ d i conslder' I 1 70 512 1 21 1; able detail with reference to certain preferred embod1- 6Q R2=2.93F 81:08 ments thereof, it will be understood that variations and modifications can be elfected without departing from the H RFAQIF T=.214F spirit and scope of the invention as described hereinabove. R 869F Sz=.067F

I claim: 1n 1. 70 56.2 5 T;=.13OF

1. A photographic objective of the simple tr1plet type R=.634F having an equivalent focal length F and comprising two outer simple positive biconvex lens elements and an mner 4 A photographic objective of the Simple triplet type simple negative biconcave lens element, the lens elements having an equivalent focal length F and comprising two f s'fbstallnauy f following charactemucs and 7 outer simple positive biconvex lens elements and an inner Ida-011$ f f lens elemePts are numbefed simple negative biconcave lens element, the lens elements from the from, N 15 the lfldex of reflactlon for the D line: having substantially the following characteristics and V 15 the lHdeX 0f dISPCI'SIOII, and T and 5 refer p spatial relations in which the lens elements are numtively to the radii of curvature of the lens surfaces, the bered from the front, N is the index of refraction for the axial thicknesses of the lens elements, and the axial spac- '7 D line, V is the index of dispersion, and R, T and S Lens N V Radii Thieknesses and spacings I 1. 49 57. 4 T =.140F

Rz= -.886F

S .041]? Ra= -.599F II 1. 57 36.6 Tz=.199F

S2= .047F R5: 7181? III 1. 61 58.8 T1= .237F

Re= .718F

5. A photographic objective of the simple triplet type having an equivalent focal length F and comprising two outer simple positive biconvex lens elements and an inner simple negative biconcave lens element, the lens elements having substantially the following characteristics and spatial relations in which the lens elements are numbered from the front, N is the index of refraction for the D line, V is the index of dispersion, and R, T and 5 refer respectively to the radii of curvature of the lens surfaces, the axial thicknesses of the lens elements, and the axial spacings between the lens elements, numbered by subscript from front to rear:

Lens N]; V Radii Thicknesses and Spacings R =J535F I 1.61 57.2 T =.l70F

Rz= 1.43F

S1 .OGZF Rs= .695F II 1. 65 33. 8 T2= .216F

Sz= .0621 R =.7l8F III 1. 61 57. 2 Ts= .184F

Ra= .608F

the axial spacings between the lens elements, numbered by subscript from front to rear:

Lens N V Radii Thieknesses and Spacings R1= .508 I 1.61 58.6 T =.195F

S .0635 Rs= .691F II 1.65 33. 9 Tz=.196F

Sz= .0741? Rs= .682F III 1. 61 58. 6 Ts= .1851

7. A photographic objective of the simple triplet type having an equivalent focal length F and comprising two outer simple positive biconvex lens elements and an inner simple negative biconcave lens element, the lens elements having substantially the following characteristics and spatial relations in which the lens elements are numbered from the front, -N is the index of refraction for the D line, V is the index of dispersion, and R, T and S refer respectively to the radii of curvature of the lens surfaces, the axial thicknesses of the lens elements, and the axial spacings between the lens elements, numbered by subscript from front to rear:

DAVID SCHONBERG, Primary Examiner. R. I. STERN, Assistant Examiner.

US. Cl. X.R. 350206 

